What motivates people's behaviour? Why is this person so keen on mountain bike riding?

The study of motivation is concerned with understanding psychological processes that drive and direct behaviour. Psychologists study motivational forces to help understand and explain patterns and changes in individual human behaviour. Motivational concepts serve several functions, including:

Understanding motivation is also important for understanding individual differences more generally. According to motivational theorists, motivation and emotion together govern human behaviour. Much empirical attention has been given to determining different aspects, or factors, of motivation.